The present invention relates to the making of samples for purposes of determining the degree of purity of metals. Within the context of this invention, metal includes iron as well as non-ferous metals and alloys thereof. It is assumed that owing to the particular metalurgical history these metals may contain undesirable impurities. Impurities within this context are essentially non-metallic phases which are deformable depending upon temperature. Their inclusion is presumed to impart undesirable properties upon the metal. It is known to inspect and test metals through ultrasonic processes, and the content of the impurities can be subsequently indicated and evaluated. Generally speaking, these tests are conducted within the frame of determining degrees of impurity.
As far as iron and iron alloys are concerned, the invention finds particular utility in the case of steel having been processed by continuous casting.
It is a general trend to increase requirements on a product, and stringent requirements include the one concerning purity as defined above. Aside from the problem of attaining the desired degree of purity, it is also a problem to determine the degree of purity in the first place. With increasing demands, it was found that standardized test methods of the past are no longer adequately reliable. This means that, to an increasing extent, failure rates of a product, either during manufacture or even on use, become a rather belated indicator of the degree of purity of the metal involved. As far as steel and metallurgical developoments generally are concerned, this is a very undesirable situation. Generally speaking, one can not expect a "feedback" between user and manufacturer, and even if such a feedback exists, say through complaints, a long delay could be expected before such feedback can be acted upon.
It is quite obvious that on a worldwide basis, there is a demand for new methods which are practical, expedient, economical and reliable as far as inspecting the degree of purity of components is concerned, a specific requirement being differentiating among areas, zones and portions of the product; another requirement is quantification. Sectionalizing involves particularly sections or portions of limited length as far as continuous casting is concerned. It is believed that the present invention meets all these requirements and constitutes a significant improvement over the art.
The following is a summary of known test methods concerning impurities. One method includes the extraction of sulphur, also known as the Bauman print method. Metallography as per a German standardized iron test sheet for steel 1570 . Step turning samples being another kind of test set forth under the number 1580. There are also known so-called blue-fracture samples; ultrasonic testing of plate-stock even if entirely along the edges, a slime extraction method, i.e. a certain residue is isolated; and quantitative metallography on relatively large plate stock areas such as areas of 200 cm.sup.2. It is beyond the scope of this discussion to detail a critique on these methods. Generally however, it can be said that as far as the present trend towards enhancing the testing degrees of impurities is concerned, these methods are no longer adequate. Owing to a clear lack of suitable pieces of equipment the problem was posed for many years that it was very difficult, even impossible, to determine by way of testing whether any particular feature used in the making and processing of steel, did or did not exhibit the desired result, except that much later when failure rates, or lack of them, became known.